Forest machine with crane

ABSTRACT

A forest machine with a crane comprises a driver&#39;s cab (2) which is mounted on a wheeled chassis (1) and behind which a load carrier (3) is placed, and a crane post (10) mounted in association with the cab and rotatable relative to the chassis and carrying an outer boom (11) having a telescopic boom (16) which is arranged at its free end to carry a working tool (21). The crane post (10) comprises two suitably inclined, spaced-apart support arms (12) between which extends a pivot shaft (13) on which the outer boom is mounted in a position between the support arms. The pivot shaft (13) is located at a distance from the center of rotation of the post (10) exceeding half the distance between a pair of wheels carrying the chassis of the machine. The outer boom is movable through at least 90° between a horizontal and a vertical position, more precisely by means of a hydraulic cylinder (19).

TECHNICAL FIELD OF THE INVENTION

This invention relates to a forest machine having a crane and being ofthe type comprising a driver's cab which is mounted on a wheeled chassisand behind which a load carrier is disposed, and a crane post mounted inassociation with said cab and rotatable relative to the chassis andcarrying an outer boom having a telescopic or extension boom movablebackwards and forwards and adapted at its free end or tip to carry aworking tool, such as a grapple, a harvester assembly, a loading hook orthe like.

BACKGROUND OF THE INVENTION

Hitherto known cranes in forest machines of the above-described typenormally comprise not only a crane post and an outer boom, but also afirst boom section which is mounted therebetween and the movements ofwhich are adjusted by means of at least one hydraulic cylinder. Thismeans that it is difficult to maneuver such cranes when operating inforest stands where it is desirable in as short a time as possible toseize and/or process the trees and place them on the load carrier of themachine, since the operator must pay attention not only to suchfunctions as the rotation of the crane post, pivotal movement of theouter boom and telescopic movement of the extension boom in relation tothe outer boom, but also to the movements of the first boom section inrelation to the crane post as well as the cooperation of the first boomsection with the outer boom. Another shortcoming inherent in prior artcranes of the above type is that they are of a complicated and, thus,expensive design.

BRIEF ACCOUNT OF THE INVENTIVE CONCEPT

The present invention aims at overcoming the above-mentioned drawbacksby providing a crane which is designed especially for forest machines,such as forwarders or harvesters, and which is easy to operate in aquick and convenient way and is of a simple and inexpensive design whilebeing robust and capable of handling heavy loads within a substantial,optimal area of operation. According to the invention, these and otherobjects are achieved by a forest machine which is characterized in thatthe crane post comprises two suitably inclined, spaced-apart supportarms between which a shaft extends which serves as a pivot and on whichthe outer boom is mounted in a position between, preferably midwaybetween said arms, that said shaft is located at a distance from thecentre of rotation of said post exceeding half the distance between apair of front wheels carrying the chassis of the machine, and that theouter boom is movable through at least 90° between a substantiallyhorizontal position and a substantially vertical position, moreprecisely by means of at least one power mechanism, particularly ahydraulic cylinder, whereby the boom tip is movable not only within anarea substantially completely covering the volume of the load carrier,but also to positions close to both sides and the front of the cab aswell as the ground surrounding the machine.

U.S. patent specification No. 3,265,219 describes a crane which isintended for a truck and which, in addition to a rotatable frame in theform of a post and a first boom section which is pivotal in relation tothe post, comprises an outer boom which is pivotal to a limited extentrelative to the first boom section and which is articulated in a pointlocated outside or at the side of the wheels of the vehicle. In thisconstruction, the outer boom is however laterally offset with respect tothe first boom section so as to be capable, when moved to a parkingposition, of moving beside both the first boom section and the post. Inpractice, this laterally offset location of the outer boom relative tothe first boom section means that the crane is ill-suited for handlingsuch heavy loads as trees, since in such a case extremely large torquesare applied to the crane in the area between the outer boom and thefirst boom section. Further, the known crane has a limited range ofoperation. For instance, the working tool employed cannot be placed infront of the driver's cab.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the drawings,

FIG. 1 is a schematic side view of a forest machine having a cranedesigned in accordance with the invention,

FIG. 2 is a schematic top plan view of the machine or vehicle,

FIG. 3 is a simplified perspective view illustrating one embodiment ofthe crane on a larger scale,

FIG. 4 is an end view from in front of the forest machine in FIG. 1, and

FIG. 5 is a partial side view showing an alternative embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In FIGS. 1 and 2, numeral 1 generally designates the chassis or frame ofa forest machine in the form of a forwarder having a driver's cab 2 anda load carrier or bin 3 disposed behind the cab. In the illustratedexample, the chassis 1 is carried on three pairs of wheels 4, 5, 6 ofwhich two front wheels 4, 5 located on the same side are mounted oncommon yokes 7, thus forming bogies which are individually pivotablerelative to the chassis in the manner disclosed in SE patent application8600123-7. The vehicle may also in other respects regarding chassis,wheel suspensions and load carrier be devised in the manner disclosed insaid patent application. Especially, it may be provided withdouble-pivot steering in that the two rear wheels 6 arependulum-suspended in relation to the chassis and pivotal in relation tothe swing arms employed.

The cab 2, together with an associated drive unit 8, is rotatablerelative to the chassis 1 by means of a gear rim 9 or the like.Suitably, the cab is rotatable one revolution or at least approximately360°, such that the front window of the cab can be oriented in anydesired angular position relative to the centre of rotation designated Cin FIG. 1. In this context, it should also be noted that the dimensionsof the cab and the drive unit are such that--regardless of their angularposition--they will never project appreciably from the base surfacedefined, on the one hand, by the width of the vehicle (i.e., thedistance between the outer sides of opposite wheels) and, on the otherhand, by the distance between the front end of the load carrier 3 andthe front portion of the chassis 1.

The cab 2 is associated with a crane post, generally designated 10,which carries an outer boom 11. As best seen in FIG. 3, the post 10comprises two spaced-apart, suitably parallel support arms 12, 12'between which there extends a shaft generally designated 13 on which theouter boom 11 is mounted. In the illustrated embodiment, the supportarms 12, 12' are connected with side members 14, 14' which, togetherwith a base member 15, form a frame which encloses the cab and isrotatable together therewith by means of the gear rim 9. In other words,the crane post 10 is also rotatable relative to the above-mentioned axisof rotation C, suitably one revolution or approximately 360°. The sidemembers 14, 14' also serve as a safety frame for the cab 2.

The outer boom 11 also includes at least one further boom or extensionboom 16 which is movable backwards and forwards relative to the outerboom 11 for moving a tool attachment 17 towards and away from the shaft13 (see arrow A). In the embodiment illustrated in the drawing, the boom16 is a box section inserted in a slightly larger box section formingthe outer boom 11. The boom 16 is telescopically movable in the boom 11by means of a double-acting piston and cylinder assembly 18 integratedin the two box sections. It should here by emphasized that theillustrated embodiment is only one of several conceivable designs. Thus,the telescoping boom 16 may be replaced by a sliding boom or any otherconstruction which is adapted, in the manner described above, to movethe tool attachment 17 towards and away from the shaft 13. It is alsoconceivable to use a plurality of booms telescopically mounted in eachother, for instance when it is desired to have a crane with an extremelylarge range of operation.

In the illustrated embodiment, the pivot shaft 13 comprises two halvesor sections 13', 13" each of which is rigidly connected at one end tothe outer boom or box section 11 and rotatably mounted at their oppositeend relative to the associated support arm. In practice, the shaftsections 13', 13" may consist of tubes welded to the box section andmounted on rod members fixedly connected to the support arms. Forpivoting the outer boom 11, there is provided in this embodiment, oneach side of the boom a double-acting hydraulic cylinder 19 which at oneend is suitably articulated to the associated support arm 12 at the rearend thereof, while the opposite end, here the free end of the pistonrod, is articulated to a lug 20. In the state shown in FIG. 3 where theouter boom 11 is in a horizontal position, the lug 20 is directedobliquely downwardly-forwardly from the centre of the shaft. Thus, theouter boom can be pivoted within a very large angular range by means ofa relatively short hydraulic cylinder.

Reference is again made to FIG. 1 from which it appears that the portion11' of the outer boom 11 located behind the pivot shaft 13 issubstantially longer than the outer boom portion 11" extending forwardlyof the pivot shaft. In practice, the portion 11' may be 2-3, suitablyabout 2.5 times longer than the portion 11". From FIG. 1 further appearsthat the distance G between the centre of rotation C of the crane postand the pivot shaft 13 exceeds the distance D between said centre ofrotation and the front end or end wall of the load carrier 3. Thedistance D essentially corresponds to the distance D' between the centreof rotation of the crane post and the front end of the chassis 1, thedistance (D+D') between the front end wall of the load carrier and thefront end of the chassis 1 essentially corresponding to the width B ofthe vehicle (counted as the distance between the outer sides of oppositewheels). By this geometry, it is ensured that the shaft 13, as shown inFIG. 1, will be located in the area behind the front end wall of theload carrier when the crane post is rotated straight backwards relativeto its centre of rotation. As further appears from FIG. 4, the shaft 13is located outwardly of the outer side of the wheels when the post isswung sideways from the vehicle. Similarly, the pivot shaft will belocated in the area in front of the forward end of the chassis 1 whenthe post is swung straight forwards relative to its centre of rotation.As clearly appears from FIG. 4, a grapple 21, mounted in the toolattachment of the extension boom 16, may thus be located very close tothe vehicle when the outer boom 11 is pivoted to a vertical position. Inthis position, the grapple can also reach as far as the ground.Similarly, the grapple may of course also be located at ground leveljust in front of the chassis.

As appears from FIG. 1, the support arms 12 extend obliquely in relationto the horizontal plane, such that the shaft 13 will be at a certaindistance above the cab 2. In practice, the support arms may be inclinedabout 20°-30°, suitably about 25°, in relation to the horizontal plane,whereby the outer boom can be pivoted upwards a considerable distance inthe anticlockwise direction from the horizontal position indicated infull lines, more precisely suitably about 15°-30° from this position. Asfurther appears from the sweep curve shown in dash-dot lines, the outerboom can be pivoted downwards not only through 90° from the horizontalposition indicated in full lines, to a substantially vertical positionbut through a further distance of at least about 5°-10°. From FIG. 1further appears that the length H of the front portion 11" of the outerboom is considerably less than the distance I between the shaft 13 andthe top of the load carrier 3.

It appears from the foregoing that the grapple 21, by adjustment of thepivotal movement of the outer boom and the position of displacement ofthe extension boom 16 relative to the outer boom, can reach practicallyany point within the load carrier 3, the grapple being laterallypositioned by rotating the crane post 10 about its centre of rotation.

The embodiment illustrated in FIG. 5 differs from the previouslydescribed embodiment only in that the grapple has been replaced by aharvester or processor assembly 21'. Also, the support arms 12 formingthe crane post are mounted on a gear rim or the like 9' disposed on topof the cab 2' which in this case is fixedly mounted on the vehiclechassis. It should also be noted that the lugs 20' for the hydrauliccylinders 19' are directed upwards from the pivot shaft 13, thehydraulic cylinders being connected at their rear ends to upwardlyprojecting attachments 22 by means of which the cylinders are located ata certain distance above and substantially parallel to the support arms.In this case, too, the crane post comprises two side members 23enclosing the cab and serving as a safety frame therefor. In thisinstance, the safety frame is however not directly connected to thesupport arms 12 but carries the gear rim 9' in turn carrying the supportarms.

ADVANTAGES OF THE INVENTION

The crane design described above is very easy and inexpensive tomanufacture, primarily since it includes but a single articulation, i.e.the pivot shaft 13 for pivoting the outer boom. This feature makes itextremely easy for the operator to maneuver the crane because only threefunctions need be observed, viz.:

(a) rotation of the post 10 about the centre of rotation C,

(b) pivotment of the outer boom 11 upwards or downwards, and

(c) displacement of the extension boom 16 out of or into the outer boom11.

When the tool attachment or extension boom tip is being moved todifferent spatial points, all movements are at right angles or parallelto the boom tip. While the crane is of a simple design, it has arelatively large range of operation and a substantial flexibility inthat the boom tip can reach not only practically any point in the loadcarrier but also any point in the immediate vicinity of the outer sideof the vehicle and of the ground. Thanks to the suitably centriclocation of the outer boom between two support arms, there is obtained arobust crane capable of handling heavy loads without the need of anyoversized constructional elements. The fact that the major part of theouter boom 11 (portion 11') is located behind the shaft 13 further meansthat this part will serve as a counterweight for the extension boom 16and, hence, the pivotal movements of the outer boom can be executed verysmoothly. It should also be pointed out that the crane may easily beautomated and also may be placed both in front of the cab and behind iton the load carrier. Further, it should be noted that the workingconditions of the driver are essentially improved ergonomically when thecab is rotatable together with the crane, as shown in the embodiment ofFIGS. 1-4. In this case, the driver seldom or never need execute tiringtwisting and turning movements of the body, especially of the head, whenmaneuvering the crane, which is of substantial physiological importanceduring continuous long-term operations. Using parts of the crane post assafety frame for the cab further means that the cab can be manufacturedcheaply. Finally, it should be pointed out that the driver, whenmaneuvering the crane, may pay full attention to the position of theworking tool and need not bother about how the other parts of the craneaffect the forest stand since the rear portions of the outer boom arealways within the base area of the cab irrespective of the position ofrotation of the crane.

POSSIBLE MODIFICATIONS OF THE INVENTION

It goes without saying that the invention is not restricted only to theembodiments described above and illustrated in the drawings. Thus, it isconceivable, for instance, to use a single hydraulic cylinder, insteadof two such cylinders, for pivoting the outer boom. Further, the designof the crane post may be varied in several different ways. For instance,the pivot shaft 13 may extend through the outer boom 11, in which casethe extension boom 16 moves in a plane separate from that of the shaft.Also, it is conceivable to arrange the support arms 12 such that theycan be adjusted to different working positions in respect of theirinclination relative to the horizontal plane, e.g. for temporarilyreducing the overall height of the vehicle, thus making it possible torun the vehicle under viaducts or the like.

As to the sweep curve shown in FIG. 1, it should be pointed out that itrelates to the tip of the crane boom or the free end of the extensionboom 16. In practice, the actual reach of the crane will of courseincrease by the length of the working tool 21 and 21' connected to theboom. This also applies to the working area surrounding the forestmachine, which is indicated in FIG. 2 by a circle K.

I claim:
 1. A crane-type forest machine comprising a crane and a wheeledchassis having width, length and depth dimensions, sides and a front,the chassis having at least a pair of opposed, spaced apart frontwheels, a driver's cab mounted on said wheeled chassis over said frontwheels; a load carrier having a length disposed behind said cab and onthe chassis; a rotatable crane post mounted for rotation about avertical axis, relative to said chassis; said crane post comprising apair of spaced apart upwardly extending arms, one on each side of thecab, each of said arms including an inclined end portion, said endportions extending in spaced apart relationship; a rotatable shaftextending transversely between said inclined end portions and beingrotatable about a horizontal axis; means for rotating said shaft aboutsaid horizontal axis; said shaft being spaced above and positioned adistance from said vertical axis greater than the minimum distance fromsaid vertical axis to the sides and front of said chassis; a boommounted intermediate its ends on said shaft whereby said boom isrotatable about said horizontal axis; an extension boom associated withsaid boom; and means for extending and retracting said extension boom;whereby said arms can be pivoted about said vertical axis and said boompivoted about said horizontal axis to extend vertically at any positionalong said sides and front of the chassis to reach the ground level atthe sides and front of the chassis.
 2. A forest machine as claimed inclaim 1, characterized in that said crane post is connected to said caband is rotatable therewith relative to said chassis.
 3. A forest machineas defined in claim 2, wherein said crane post and cab are rotatablethrough 360°.
 4. A forest machine as claimed in claim 1, wherein saidinclined end portions form an extension of said arms.
 5. A forestmachine as claimed in claim 1 wherein said extension boom is atelescopic boom.
 6. A forest machine as claimed in claim 1 wherein saidextension boom has a free end adapted to mount a working tool selectedfrom the group consisting of a grapple, a processor assembly and aloading hook.
 7. A forest machine as claimed in claim 1 wherein saidboom is mounted midway between said inclined end portions.
 8. A forestmachine as claimed in claim 1 wherein said means for rotating said shaftcomprises a hydraulic cylinder.
 9. A forest machine as claimed in claim1, wherein said arms are arranged on both sides of said cab and form asafety frame therefor.
 10. A forest machine as claimed in claim 1,wherein said cab has opposed sides and a front, and wherein theextension boom has a free end movable to a first position within thedimensions of said load carrier, and to a second position in areasadjacent said opposed sides and said front of said driver's cab, and toa third position close to a substrate upon which said forest machine isbeing operated.
 11. A forest machine as claimed in claim 1, wherein saidboom has a rear portion and a front portion, said rear portion extendingrearwardly of said rotatable shaft and has a length which at leastsubstantially corresponds to the length of a distance between said frontwheels, said boom having a front portion extending forwardly of saidrotatable shaft and having a length less than the length of said rearportion of said boom.
 12. A forest machine as claimed in claim 11,wherein said front portion of said boom and said extension boom have atotal length at least equal to the length of said load carrier.
 13. Aforest machine as claimed in claim 11, wherein said load carrier hasdepth dimensions defined by a top and a bottom of said load carrier, andwherein the length of said front portion of said boom is less than avertical distance extending between said rotatable shaft and the top ofsaid load carrier.
 14. A forest machine as claimed in claim 11, whereinsaid rotatable shaft comprises a pivot shaft having a pair of sections,each section having opposed ends, one end of each section being rigidlyconnected to said boom, and the opposed end being rotatably mountedrelative to said inclined end portions, said machine further including adouble-acting hydraulic cylinder having opposed ends, said double-actinghydraulic cylinder being mounted at one end to each section of saidpivot shaft and at the opposed end to said crane post.
 15. A forestmachine as claimed in claim 14, wherein said double-acting hydrauliccylinder is connected to said shaft sections via a lug whereby when saidboom is in a substantially horizontal position, said lug extendsobliquely downwardly and forwardly from said pivot shaft, and at saidopposed end, said hydraulic cylinder is connected to said crane post viaan articulation disposed in said inclined end portions.
 16. A forestmachine as defined in claim 1 wherein the length of said rear portion ofsaid boom exceeds the length of said distance between said front wheels.17. A forest machine as defined in claim 12 wherein said total lengthexceeds the length of said load carrier.
 18. A forest machine as definedin claim 12, wherein said total length is at least equal to a verticaldistance extending between said rotatable shaft and said substrate. 19.A forest machine as defined in claim 14, wherein said hydraulic cylinderis mounted to said inclined end portions.